Question

Calculate Re for 1.47m tall person swimming in water at 0.2ms^-1. Viscosity of water is 1.0cp= 1x10^-3

Calculate Re for a 1.35m tall person swimming in butter at 0.03ms^-1. The density of the butter is 1.3x10^3kgm^-3

Calculate the Re for a 1.0µm of a bacteria swimming in water at 19.0µm^-1

Answer 1

We know Reynolds number,   where is the density of fluid , L is the linear dimension of the object, v is the velocity of the fluid with respect to the object and is the viscosity of the fluid.

(a) Here L = hight of the man = 1.47 m , v = 0.2 m/s , viscosity of water = 1.0 cp = , density of water

So R the Reynolds number is

(b) Here L = 1.35 m , v = 0.03 m/s , Density of butter

We know viscosity of butter

So the Reynolds number in swimming in butter is 0.2106.

(c) length of the bacteria ,

velocity ,

So the Reynolds number when a bacteria swims is